You’re forgetting the fact that they still play the same role: to primarily deal damage.
If tanks and supports were split into the sub categories off tanks and off supports then would it suddenly make them two different roles? If so then this would still result in less heroes in each tank/support related category.
Also, this organization was removed from the game for a reason. Everyone considered defensive and offensive as the same role (dps) anyway. Stop pretending like they’re super different just because of the organization.